Lightweight submarine cable structure and method for manufacturing electrical units thereof

Abstract

The application belongs to the technical field of submarine cables, and particularly relates to a lightweight submarine cable structure and a preparation method of an electric unit of the submarine cable structure. The submarine cable structure comprises a three-core electric unit. The electric unit comprises a conductor layer, an insulating layer and a metal shielding layer. The metal shielding layer comprises an inner shielding layer, an outer shielding layer and an aluminum-plastic composite tape layer arranged in sequence from inside to outside. By increasing the pitch ratio, the axial gap between adjacent copper wires is increased, the copper wires are arranged loosely, the overall flexibility of the cable is improved, the copper wire layer is not easy to deform or debond during bending, and thus the protection requirement for the lead sheath is weakened, so that the thickness of the lead sheath can be omitted, weight reduction is achieved, a larger lap rate is adopted, the cooperation between the outer layer of the winding mesh belt and the axial increased gap between the copper wires is facilitated, the outer layer of the winding mesh belt partially penetrates into the gap and partially gradually transitions to the adjacent copper wires, the physical concave-convex form engagement between the two layers is achieved, the engagement force is increased, and the stability is improved.

Description

Technical Field

[0001] This invention belongs to the field of submarine cable technology, specifically relating to a lightweight submarine cable structure and a method for preparing its electrical units. Background Technology

[0002] In the field of traditional offshore ultra-high voltage (typically 220kV~500kV) power transmission, three-core submarine cables play a crucial role in high-capacity, long-distance power transmission. Traditional ultra-high voltage three-core submarine cables typically employ a heavy structure and high-density materials to meet requirements for electrical performance, mechanical strength, waterproofing, and corrosion resistance. Traditional submarine cables often use copper conductors, limiting the choice of insulation materials. Lead sheaths are commonly used, and while the metal armor provides mechanical protection, it also increases weight, leading to an overall increase in cable weight that is difficult to reduce, hindering transportation and installation.

[0003] It should be noted that this part of the present invention only provides background technology related to the present invention, and does not necessarily constitute prior art or known technology. Summary of the Invention

[0004] The purpose of this invention is to provide a lightweight submarine cable structure and a method for manufacturing its electrical units, so as to solve the problem of increased weight caused by the use of lead sheaths and excessively thick insulation layers in existing submarine cables.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a lightweight submarine cable structure, comprising a three-core electrical unit, wherein the electrical unit includes:

[0006] Conductive layers are used to conduct electricity to enable power transmission;

[0007] An insulating layer, covering the outside of the conductor layer, is used to insulate the conductor layer;

[0008] A metal shielding layer, which covers the outside of the insulating layer, is used to shield the high-voltage electric field of the conductor layer. The metal shielding layer includes an inner shielding layer, an outer shielding layer, and an aluminum-plastic composite tape layer arranged sequentially from the inside to the outside. The inner shielding layer includes multiple copper wires spirally wound on the insulating layer, with a pitch ratio of 7 to 9:1 between the copper wires. The outer shielding layer is a semi-conductive copper wire shielding tape, which is wrapped around the inner shielding layer in a semi-overlapping manner, with an overlap rate of 50% to 80%.

[0009] In one possible implementation, the winding angle of the semi-conductive copper wire shielding strip is 15~30°, the width of the semi-conductive copper wire shielding strip is 60~90mm, and the thickness of the semi-conductive copper wire shielding strip is 0.3mm~0.7mm.

[0010] In one possible implementation, the volume resistivity of the semiconductive copper wire shielding strip is ≤600Ω·cm, and the surface resistivity is ≤1700Ω.

[0011] In one possible implementation, the elongation of the semiconductive copper wire shielding strip is greater than or equal to 3%.

[0012] In one possible implementation, the semiconductive copper wire shielding strip comprises multiple galvanized copper wires, the number of which is 10 to 30, the diameter of which is 0.1 mm to 0.3 mm, and the weight of each galvanized copper wire is ≤460 g / m. 2 .

[0013] In one possible implementation, the aluminum-plastic composite tape layer is longitudinally wrapped around the outer shielding layer with hot melt adhesive, and the tension variation range of the wire wrapped by the aluminum-plastic composite tape layer is controlled within ±10%.

[0014] In one possible implementation, the hot melt adhesive has a dispensing rate of 0.1~0.5L / min and a hot melt temperature of 80~120℃.

[0015] Optionally, the hot melt adhesive includes at least one of the following parameters:

[0016] The softening point of the hot melt adhesive is 82~96℃;

[0017] The melt viscosity of the hot melt adhesive is 10,000 to 14,000 CPs;

[0018] The curing time of the hot melt adhesive is 6-8 seconds;

[0019] The open time of the hot melt adhesive is 8-10 seconds.

[0020] In one possible implementation, the electrical unit further includes: a non-metallic sheath; the non-metallic sheath is disposed outside the metallic shielding layer; the non-metallic sheath is a semi-conductive polyethylene sheath.

[0021] In one possible implementation, the lightweight submarine cable structure further includes: an armor pad, an armor layer, and an outer pad layer sequentially covering the three-core electrical unit; a filling layer is provided between the armor pad and the electrical unit; the armor pad and the outer pad layer are made of PP rope.

[0022] In one possible implementation, the insulating layer is a polymer matrix dispersed with nanoscale insulating reinforcing particles, the total amount of the nanoscale insulating reinforcing particles being ≤4.5wt%; the nanoscale insulating reinforcing particles include nanoscale silica particles and nanoscale boron nitride particles, the ratio of the nanoscale silica particles to the nanoscale boron nitride particles being 4~6:1.

[0023] Optionally, the polymer matrix is ​​cross-linked polyethylene, and the polymer matrix includes at least one of the following parameters:

[0024] Dielectric strength ≥ 35MV / m;

[0025] Dielectric loss factor ≤ 5.0 × 10 -4 ;

[0026] Volume resistivity ≥ 1.0 × 10 14 Ω.m.

[0027] Secondly, embodiments of the present invention also provide a method for fabricating an electrical unit, used to fabricate an electrical unit for a lightweight submarine cable structure as described in the first aspect, the fabrication method comprising:

[0028] S100, providing a conductor layer, and covering the conductor layer with an insulating layer;

[0029] S200: Copper wire is spirally wound around the outside of the insulation layer at a preset pitch ratio to form an inner metal shielding layer;

[0030] S300, a semi-conductive copper wire shielding strip is wrapped around the inner metal shielding layer with a preset overlap rate to form an outer metal shielding layer;

[0031] S400, an aluminum-plastic composite strip layer is longitudinally wrapped around the outer shielding layer, and hot melt adhesive is used to bond the aluminum-plastic composite strip layer to the outer shielding layer, thereby forming an electrical unit.

[0032] The present invention has at least the following beneficial effects:

[0033] The lightweight submarine cable structure and its electrical unit preparation method provided by this invention, the metal shielding layer of the submarine cable structure, by increasing the pitch ratio (equivalent to reducing the winding angle), makes the copper wires wound more smoothly, the helix longer, and the axial gap between adjacent copper wires larger; the copper wires are loosely arranged, improving the overall flexibility of the cable, and the copper wire layer is not easily deformed or debonded when bent, thereby reducing the need for lead sheath and other protection, thus facilitating the elimination of lead sheath thickness and achieving weight reduction; maintaining a suitable pitch avoids excessive concentration of shielding effect and also helps to reduce shielding layer resistance and reduce shielding circulating current loss.

[0034] Furthermore, increasing the pitch ratio provides better shielding, but the larger gaps between the inner copper wires may cause electric field concentration or non-uniformity. By wrapping the semi-conductive copper wire shielding tape around the copper wire with an overlap rate of at least 50%, an outer metal shield is formed. A tighter overlap rate creates a more continuous, dense, and relatively smooth conductor layer, providing a better equipotential surface and ensuring a more uniform radial electric field on the outer surface of the insulating shield at any location (including above the gaps between copper wires), thus improving electric field uniformity. Using an overlap rate greater than 50% (50%~80% in this embodiment, optionally 52%~65%) facilitates the formation of locally layered protrusions and gradually varying thickness areas, thereby facilitating the fit between the outer winding mesh tape and the copper wires with an increased axial gap. The outer winding mesh tape partially penetrates the gap and partially transitions to adjacent copper wires, achieving… The physical interlocking between the two layers increases the interlocking force, improves stability, and also provides local corrugated buffering, enhancing the cable's resistance to deformation such as bending. It significantly eliminates potential electric field concentration or inhomogeneity caused by gaps in the inner copper wires, suppressing partial discharge. The mesh of the semi-conductive copper wire shielding tape provides additional parallel paths for short-circuit currents between the copper wires, as well as short-circuit current paths along the copper wires. Through different conductivity forms and the transition of composite conductivity forms in the contact area between the two layers, the short-circuit current carrying capacity is greatly improved, making it easier to maintain a better electric field environment under the non-metallic sheath and reducing cable weight. The high overlap rate achieves a better mechanical interlocking effect, greatly enhancing the integrity and stability of the tape layer, preventing displacement, warping, or loosening of the tape during subsequent processing or cable bending. The improved shielding performance allows for a reduction in the thickness of the internal insulation layer, achieving cable lightweighting.

[0035] Furthermore, the lightweight submarine cable structure design allows for a narrower submarine route, reducing the area occupied by the cable and lowering investment costs. Additionally, due to the close proximity and symmetrical structure of the three phases, the electromagnetic fields are essentially canceled out internally, resulting in minimal external electromagnetic radiation. The metal sheath and armor layer are typically grounded at both ends, leading to low induced current, low operating losses, reduced transmission losses, energy savings, extended service life, and reduced maintenance costs. Attached Figure Description

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1This is a schematic diagram of a cross-sectional structure of a lightweight submarine cable structure provided in an embodiment of the present invention;

[0038] Figure 2 This is a schematic diagram of the specific structure of the metal shielding layer provided in the embodiment of the present invention;

[0039] Figure 3 This is a flowchart illustrating a method for fabricating an electrical unit of a lightweight submarine cable structure according to an embodiment of the present invention.

[0040] In the diagram: 1-Conductor layer; 2-Insulation layer; 3-Metallic shielding layer; 310-Inner shielding layer; 320-Outer shielding layer; 330-Aluminum-plastic composite tape layer; 4-Non-metallic sheath; 5-Filling layer; 6-Armor padding layer; 7-Armor layer; 8-Outer padding layer. Detailed Implementation

[0041] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0043] It should be further understood that the term "comprising" as used in this specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The term "and / or" as used herein includes all or any unit and all combinations of one or more associated listed items.

[0044] The first aspect, such as Figure 1As shown, this embodiment of the invention provides a lightweight submarine cable structure, mainly used for ultra-high voltage power transmission. This lightweight submarine cable structure specifically includes a three-core electrical unit (a three-core electrical unit refers to three electrical units; this invention uses a tightly symmetrical three-core stranding method to reduce unnecessary filler material and support structure). Each electrical unit specifically includes, from the inside out: a conductor layer 1, an insulation layer 2, and a metal shielding layer 3. The conductor layer 1 conducts electricity to achieve power transmission. The insulation layer 2 covers the outside of the conductor layer 1 and serves to insulate it. The metal shielding layer 3 covers the outside of the insulation layer 2 and serves to shield the high-voltage electric field of the conductor layer 1, as well as the short-circuit fault current when a single-phase ground fault occurs in the system.

[0045] Specifically, such as Figure 2 As shown, the metal shielding layer 3 includes an inner shielding layer 310, an outer shielding layer 320, and an aluminum-plastic composite tape layer 330 arranged sequentially from the inside to the outside. The inner shielding layer 310 includes multiple copper wires spirally wound on the insulating layer 2, with a pitch ratio of 7 to 9:1 between the copper wires. The outer shielding layer 320 is a semi-conductive copper wire shielding tape, which is wrapped around the inner shielding layer 310 in a semi-overlapping manner, with an overlap rate of 50% to 80%.

[0046] This invention increases the pitch ratio (reducing the winding angle) to make the copper wire winding smoother, the spiral longer, and the axial gap between adjacent copper wires larger. The loose arrangement of the copper wires improves the overall flexibility of the cable, making the copper wire layer less prone to deformation or detachment when bent. This reduces the need for protection such as lead sheaths, thus facilitating the reduction of lead sheath thickness and achieving weight reduction. Maintaining a suitable pitch avoids excessive concentration of shielding effect and also helps to reduce shielding layer resistance and reduce shielding circulating current loss.

[0047] Furthermore, a larger pitch ratio provides better shielding, but the larger gaps between the inner copper wires may cause electric field concentration or non-uniformity. By wrapping the semi-conductive copper wire shielding tape around the copper wire with an overlap rate of at least 50%, an outer metal shield is formed. A tighter overlap rate creates a more continuous, dense, and relatively smooth conductor layer, which provides a better equipotential surface for the outer layer. This ensures that the electric field on the outer surface of the insulating shielding layer has a uniform radial electric field at any location (including above the gaps between the copper wires), improving electric field uniformity. Using an overlap rate greater than 50% (50%~80% in this embodiment, optionally 52%~65%) facilitates the formation of locally stacked protrusions and gradually varying thickness stacked areas. This facilitates the fit between the outer layer winding mesh tape and the copper wire with the increased axial gap. The outer layer winding mesh tape partially penetrates the gap and partially transitions to adjacent copper wires, achieving a better fit between the two layers. The physical interlocking mechanism increases the interlocking force and improves stability, while also providing localized corrugated buffering, enhancing the cable's resistance to deformation such as bending. It significantly eliminates any electric field concentration or inhomogeneity that might be caused by gaps between the inner copper wires, suppressing partial discharge. The mesh of the semi-conductive copper wire shielding tape provides additional parallel paths for short-circuit current between the copper wires, as well as short-circuit current paths along the copper wires. Through different conductive forms and the transition between composite conductive forms in the two-layer contact area, it greatly improves the short-circuit current carrying capacity, making it easier to maintain a better electric field environment under the non-metallic sheath 4, thus reducing cable weight. The high overlap rate achieves a better mechanical interlocking effect, greatly enhancing the integrity and stability of the tape layer, preventing displacement, warping, or loosening of the tape during subsequent processing (such as sheath extrusion) or cable bending. The improved shielding performance also helps reduce the thickness of the inner insulation layer 2, achieving cable lightweighting.

[0048] In some embodiments, the winding angle of the semi-conductive copper wire shielding tape is 15~30°, the width of the semi-conductive copper wire shielding tape is 60~90mm, and the thickness of the semi-conductive copper wire shielding tape is 0.3mm~0.7mm.

[0049] In this embodiment, by controlling the winding angle, it is matched with the inner layer with an increased pitch ratio. The two have different angles that are appropriately staggered, which is conducive to the mechanical interlocking of the inner and outer layers, improves the stability of the double-layer metal shielding layer 3, and further reduces the possibility of movement of copper wires with large spacing. This avoids the winding angle being too large or too small, because if the winding angle is too large or too small, it will not be conducive to the outer layer penetrating into the inner copper wires, and it will not be conducive to improving the mechanical interlocking of the inner and outer layers, nor will it be conducive to obtaining a uniform electric field.

[0050] Furthermore, controlling the appropriate winding width facilitates its integration with the inner copper wire shielding layer; both excessive width and excessive narrowness are detrimental to the fit between the winding width and the inner copper wire.

[0051] Furthermore, controlling the appropriate thickness of the winding tape ensures that the height of the overlapping area is neither too high nor too low, thereby improving interlayer bonding. If the height of the overlapping area is too high, the interlayer gaps in other parts will be too large after the winding tape penetrates into the gaps between the copper wires. If the height of the overlapping area is too small, it will not be conducive to increasing the penetration of the winding tape into the gaps between the copper wires. Both of these factors affect the bonding between the inner and outer layers and the uniformity of the electric field.

[0052] In some embodiments, the volume resistivity of the semiconductive copper wire shielding strip is ≤600Ω·cm, and the surface resistivity is ≤1700Ω.

[0053] In this embodiment, the use of a semi-conductive copper wire shielding strip with low volume resistivity and surface resistance ensures that the shielding strip can quickly conduct away the charge and avoid local electric field distortion; it can reduce Joule heating and avoid ablation; and it ensures that the contact resistance between the shielding strip and the copper wire is relatively low, avoiding heat generation or oxidation degradation, thereby improving the stability of the outer shielding layer 320 and thus improving the shielding effect.

[0054] In some embodiments, the elongation of the semiconductive copper wire shielding tape is greater than or equal to 3%, and optionally, the elongation of the semiconductive copper wire shielding tape is less than 15%.

[0055] In this embodiment, by controlling the elongation of the semi-conductive copper wire shielding tape within a suitable range, the adhesion between the semi-conductive copper wire shielding tape and the copper wire gap can be enhanced, the mechanical interlocking effect can be strengthened, and the uniform electric field can be achieved.

[0056] In some embodiments, the semiconductive copper wire shielding tape comprises multiple galvanized copper wires, the number of which is 10 to 30, the diameter of which is 0.1 mm to 0.3 mm, and the weight of each galvanized copper wire is ≤460 g / m. 2 It is known that the semi-conductive copper wire shielding tape contains a semi-conductive material and galvanized copper wire to form a shielding tape that achieves semi-conductive properties. The semi-conductive material is a semi-conductive polyethylene product.

[0057] In this embodiment, by optimizing the number of copper wires, the diameter of the copper wires, and controlling the weight, the number and distribution of conductive paths in the semi-conductive copper wire shielding strip are adjusted. This helps to improve the shielding effect by providing additional parallel paths for short-circuit current between the copper wires through the mesh of the semi-conductive copper wire shielding strip.

[0058] In some embodiments, the aluminum-plastic composite tape layer 330 is longitudinally wrapped around the outer shielding layer 320 with hot melt adhesive. The variation range of the wire tension covered by the aluminum-plastic composite tape layer 330 is controlled within ±10%, which helps to ensure the stability and sealing of the longitudinal wrapping structure.

[0059] Optionally, the hot melt adhesive has an output of 0.1~0.5L / min and a hot melt temperature of 80~120℃, for example, a hot melt temperature of 80℃, 100℃ or 120℃.

[0060] Optionally, the softening point of the hot melt adhesive is 82~96℃, for example: 82℃, 84℃, 86℃, 88℃, 90℃, 92℃, 94℃, 96℃.

[0061] Optionally, the melt viscosity of the hot melt adhesive is 10,000 to 14,000 CPs, for example: 10,000 CPs, 12,000 CPs or 14,000 CPs.

[0062] Optionally, the curing time of the hot melt adhesive is 6 to 8 seconds (s represents the unit of time, seconds), for example, the curing time can be 6 seconds, 7 seconds or 8 seconds.

[0063] Optionally, the open time of the hot melt adhesive is 8 to 10 seconds, for example, 8 seconds, 9 seconds or 10 seconds. The open time refers to the maximum allowable time from coating to pressing. Factors affecting the open time include coating temperature, amount of adhesive, ambient temperature and substrate temperature.

[0064] This embodiment improves the fluidity of the hot melt adhesive by using a higher temperature, resulting in stable longitudinal tension and stable compression of the composite shielding layer by the aluminum-plastic composite tape. This facilitates a tighter bond between the composite shielding layers, improving stability and electric field uniformity, thus enhancing the shielding effect. The improved shielding performance allows for a reduction in the thickness of the internal insulation layer, enabling cable weight reduction. The increased fluidity of the hot melt adhesive helps fill gaps in the composite shielding layer, achieving localized bonding between copper wires and between copper wires and semi-conductive copper wire shielding tapes. It also creates multi-angle buffering between different directions of the copper wire shielding tape and the copper wires, along with the flexibility of the hot melt adhesive, significantly increasing the stability of the metal shielding layer and ensuring a uniform electric field. Furthermore, controlling the amount of hot melt adhesive dispensed within the aforementioned range enhances the buffering effect. Moreover, further limiting the performance parameters of the hot melt adhesive improves the bonding force between the aluminum-plastic composite tape layer and the outer shielding layer, further contributing to the stability of the metal shielding layer.

[0065] In some embodiments, the electrical unit further includes: a non-metallic sheath 4; the non-metallic sheath 4 is sleeved outside the metallic shielding layer 3; the non-metallic sheath 4 is a semi-conductive polyethylene sheath, which ensures the electrical continuity of the three phases of the submarine cable, provides a uniform electric field, suppresses electric field concentration, and enables the system fault current to flow and share among the three phases of the metallic shielding layer 3.

[0066] In some embodiments, the lightweight submarine cable structure further includes: an armor pad 6, an armor layer 7, and an outer pad 8 sequentially covering the three-core electrical unit. Specifically, the armor layer 7 adopts a hybrid armor structure of non-magnetic high-strength fibers and lightweight metal wires (such as stainless steel wires). High-strength fibers such as aramid fibers serve as the main load-bearing components, providing excellent tensile strength and abrasion resistance. Lightweight metal wires are arranged at intervals to enhance mechanical protection and impact resistance. Compared to traditional steel wire armor, this structure reduces weight by 25% to 35% and significantly reduces eddy current losses in the armor layer 7, greatly improving the transmission efficiency of the submarine cable. Aramid fibers are woven into a fiber layer of a certain structure using a braiding device. Lightweight metal wires are interlaced at certain intervals within the aramid fiber braided layer to form a hybrid armor structure. Specialized equipment is used to cover the armor pad 6 with the hybrid armor layer 7, controlling the covering tension and the uniformity of the armor layer 7 thickness. Tensile strength and abrasion resistance tests are performed on the armor layer 7 to ensure its effective protection of the internal structure of the submarine cable.

[0067] Furthermore, a filling layer 5 is provided between the armor pad 6 and the electrical unit. The filling layer 5 adopts a semi-conductive fan-shaped filling strip, which fills the gap with semi-conductive filling material to eliminate partial discharge caused by air gap. At the same time, it can buffer the mechanical stress caused by cable bending or changes in seabed water pressure, thereby protecting the cable core wire. After filling, the outer layer is wrapped with adhesive tape to ensure the roundness of the cable.

[0068] Optionally, the armor pad 6 and the outer pad 8 are made of PP rope, which can improve the cushioning and wear resistance of the submarine cable structure and help extend the service life of the submarine cable.

[0069] In some embodiments, the insulating layer 2 is a polymer matrix with nanoscale insulating reinforcing particles dispersed therein, and the total amount of nanoscale insulating reinforcing particles added is ≤4.5wt%.

[0070] Optionally, the nanoscale insulating reinforcing particles include nano-silica particles and nano-boron nitride particles, wherein the ratio of the nano-silica particles to the nano-boron nitride particles is 4 to 6:1.

[0071] Optionally, the polymer matrix in this embodiment is cross-linked polyethylene (XLPE), and the polymer matrix has at least the following performance parameters: dielectric strength ≥ 35 MV / m, dielectric loss factor (at 50 Hz and 20 °C) ≤ 5.0 × 10⁻⁶. -4 Volume resistivity ≥ 1.0 × 10⁻⁶ 14 Ω.m. For example: dielectric strength of 40 MV / m, dielectric loss factor ≤ 4.0 × 10⁻⁶. -4 The volume resistivity is 2.0 × 10⁻⁶. 14 Ω.m.

[0072] In this embodiment, adding nano-silica to the insulation layer can significantly enhance tensile strength, elongation at break, reduce dielectric loss, suppress charge injection, and achieve a uniform electric field distribution at a low cost. Nano-boron nitride improves thermal conductivity, increases electrical tree initiation voltage, and enhances both thermal and electrical performance, but at a relatively high cost. Increasing the amount of nano-silica used helps to obtain better mechanical strength and a uniform electric field. At the same time, by adding nano-boron nitride particles, both thermal conductivity and electrical performance can be balanced. By limiting the material properties of the insulation layer, it is beneficial to improve the insulation performance of the insulation layer, which in turn is more conducive to improving the insulation shielding effect on the internal conductor layer, further improving the transmission efficiency and safety of the cable.

[0073] The second aspect, such as Figure 3 As shown, this embodiment of the invention provides a method for fabricating an electrical unit, used to fabricate the electrical unit of the lightweight submarine cable structure described in the foregoing embodiments. The method for fabricating the electrical unit includes the following steps S100~S400:

[0074] S100, a conductor layer 1 is provided, and an insulating layer 2 is wrapped around the conductor layer 1.

[0075] S200, copper wire is spirally wound around the outside of the insulation layer 2 at a preset pitch ratio to form an inner metal shielding layer 3.

[0076] Optionally, the pitch ratio of the copper wire is 7~9:1. Increasing the pitch ratio (reducing the winding angle) makes the copper wire winding smoother, the spiral longer, and the axial gap between adjacent copper wires larger. The loose arrangement of copper wires improves the overall flexibility of the cable, and the copper wire layer is less likely to deform or detach when bent, thereby reducing the need for protection such as lead sheath, which helps to reduce the thickness of the lead sheath and achieve weight reduction. Maintaining a larger and more suitable pitch avoids excessive concentration of shielding effect and helps to reduce the resistance of the shielding layer and reduce the circulating current loss of the shield.

[0077] S300, a semi-conductive copper wire shielding strip is wrapped around the inner metal shielding layer 3 with a preset overlap rate to form an outer metal shielding layer 3.

[0078] Specifically, the overlap rate of the semi-conductive copper wire shielding tape is 50%~80%, which facilitates the formation of locally overlapping raised areas and gradually varying thicknesses. This allows for better axial increase in the gap between the outer winding mesh tape and the copper wires. The outer winding mesh tape partially penetrates the gap and partially transitions to adjacent copper wires, achieving a physical interlocking action between the two layers. This increases the interlocking force, improves stability, and provides localized corrugated buffering, enhancing the cable's resistance to bending and other deformations. It also significantly eliminates potential electric field concentration or non-uniformity caused by gaps in the inner copper wires, suppressing partial discharge. The mesh size of the semi-conductive copper wire shielding tape... The copper wires provide additional parallel paths for short-circuit current, as well as short-circuit current paths along the copper wires. Through different conduction forms and the transition of composite conduction forms in the two-layer contact area, the short-circuit current carrying capacity is greatly improved, which is more conducive to maintaining a better electric field environment under the non-metallic sheath 4 and reducing cable weight. The high overlap ratio can achieve a better mechanical interlocking effect, which greatly enhances the integrity and stability of the tape layer and prevents the tape from shifting, curling or loosening during subsequent processing (such as sheath extrusion) or cable bending. The improved shielding performance helps to reduce the thickness of the internal insulation layer 2 and achieve cable lightweighting.

[0079] S400, the aluminum-plastic composite strip layer 330 is longitudinally wrapped around the outer shielding layer 320, and hot melt adhesive is used to bond the aluminum-plastic composite strip layer 330 to the outer shielding layer 320, thereby forming an electrical unit.

[0080] It should be noted that the embodiments of the present invention only introduce the preparation method of a single electrical unit. The entire submarine cable structure is provided with three-core electrical units (three electrical units are arranged symmetrically), then filled, and finally the armor layer 7 and other structures are prepared to protect the internal electrical units.

[0081] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0082] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0083] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. In the description of this specification, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lightweight submarine cable structure, comprising a three-core electrical unit, characterized in that, The electrical unit includes: Conductive layers are used to conduct electricity to enable power transmission; An insulating layer, covering the outside of the conductor layer, is used to insulate the conductor layer; A metal shielding layer, which covers the outside of the insulating layer, is used to shield the high-voltage electric field of the conductor layer. The metal shielding layer includes an inner shielding layer, an outer shielding layer, and an aluminum-plastic composite tape layer arranged sequentially from the inside to the outside. The inner shielding layer includes multiple copper wires spirally wound on the insulating layer, with a pitch ratio of 7 to 9:1 between the copper wires. The outer shielding layer is a semi-conductive copper wire shielding tape, which is wrapped around the inner shielding layer in a semi-overlapping manner, with an overlap rate of 50% to 80%. The semi-conductive copper wire shielding tape has a winding angle of 15~30°, a width of 60~90mm, and a thickness of 0.3~0.7mm; its volume resistivity is ≤600Ω·cm, and its surface resistivity is ≤1700Ω; its elongation is greater than or equal to 3%; the semi-conductive copper wire shielding tape comprises multiple galvanized copper wires, with 10~30 wires having a diameter of 0.1mm~0.3mm, and each galvanized copper wire having a single weight ≤460g / m². 2 .

2. The lightweight submarine cable structure according to claim 1, characterized in that, The aluminum-plastic composite tape layer is longitudinally wrapped around the outer shielding layer with hot melt adhesive, and the tension variation range of the wire wrapped by the aluminum-plastic composite tape layer is controlled within ±10%.

3. The lightweight submarine cable structure according to claim 2, characterized in that, The hot melt adhesive has a dispensing rate of 0.1~0.5L / min and a hot melt temperature of 80~120℃.

4. The lightweight submarine cable structure according to claim 3, characterized in that, The hot melt adhesive includes at least one of the following parameters: The softening point of the hot melt adhesive is 82~96℃; The melt viscosity of the hot melt adhesive is 10,000 to 14,000 CPs; The curing time of the hot melt adhesive is 6-8 seconds; The open time of the hot melt adhesive is 8-10 seconds.

5. The lightweight submarine cable structure according to any one of claims 1 to 4, characterized in that, The electrical unit further includes: a non-metallic sheath; the non-metallic sheath is fitted over the outside of the metallic shielding layer; the non-metallic sheath is a semi-conductive polyethylene sheath.

6. The lightweight submarine cable structure according to claim 5, characterized in that, Also includes: An armor pad, an armor layer, and an outer pad are sequentially wrapped around the three-core electrical unit; a filling layer is provided between the armor pad and the electrical unit; the armor pad and the outer pad are made of PP rope.

7. The lightweight submarine cable structure according to claim 6, characterized in that, The insulating layer is a polymer matrix dispersed with nano-sized insulating reinforcing particles, and the total amount of the nano-sized insulating reinforcing particles added is ≤4.5wt%. The nanoscale insulating reinforcing particles include nano-silica particles and nano-boron nitride particles, with a ratio of nano-silica particles to nano-boron nitride particles of 4~6:

1.

8. The lightweight submarine cable structure according to claim 7, characterized in that, The polymer matrix is ​​cross-linked polyethylene, and the polymer matrix includes at least one of the following parameters: Dielectric strength ≥ 35MV / m; Dielectric loss factor ≤ 5.0 × 10 -4 ; Volume resistivity ≥ 1.0 × 10 14 Ω.m.

9. A method for preparing an electrical unit, characterized in that, The method for fabricating an electrical unit for a lightweight submarine cable structure as described in any one of claims 1 to 8 comprises: S100, providing a conductor layer, and covering the conductor layer with an insulating layer; S200: Copper wire is spirally wound around the outside of the insulation layer at a preset pitch ratio to form an inner metal shielding layer; S300, a semi-conductive copper wire shielding strip is wrapped around the inner metal shielding layer with a preset overlap rate to form an outer metal shielding layer; S400, an aluminum-plastic composite strip layer is longitudinally wrapped around the outer shielding layer, and hot melt adhesive is used to bond the aluminum-plastic composite strip layer to the outer shielding layer, thereby forming an electrical unit.

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